Mathematical approach for two component modeling of salep-starch mixtures using central composite rotatable design: Part II. Dynamic oscillatory shear properties and applicability of Cox-Merz rule

Abstract

Dynamic shear rheological properties of salep-corn starch mixture (SCSM), salep-wheat starch mixture (SWSM) and salep-potato starch mixture (SPSM) samples were determined using a 2-factor-5-level Central Composite Rotatable Design (CCRD). Salep increased loss modulus (G '') values, and decreased loss tangent (tan delta) values of only SCSM; however, all starch types increased the storage (G'), loss (G ''), complex (G*) modulus, complex viscosity (eta*) values and decreased tan d values. At various salep and starch combination levels, a remarkable synergistic effect was observed in the dynamic shear properties. Potato starch exhibited completely different rheological performance in terms of G', G '' and eta* values. Salep did not obey the Cox-Merz rule; however, a modified Cox-Merz rule was applicable for SCSM and SPSM samples. The ridge analysis revealed that maximum G', G '', eta* and G* values for the SCSM, SWSM and SPSM samples would occur at salep = 0.54% and 0.26%, respectively, and each starch type = 2.83%. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.